Discussion Topic

On a couple of occasions I have speculated that people may react negatively to snakes because we were once their prey. I assumed it was at our tree shrew evolutionary stage, a creature similar to squirrels. Based upon the development of certain neural structures in monkeys, evidence suggests this developed later in our evolutionary path.

If so, our aversion today is caused by genetic evolution long before we developed into our present form.

This monkey wasn't as adept as others at detecting a nearby snake, and paid the price. Scientists say the evolutionary arms race between primate and snake may have led to brain structures in humans tailored to identify a snake.

By Geoffrey Mohan
October 28, 2013, 12:25 p.m.
We’re not born with a fear of snakes, but it sure seems to develop early.

Now scientists may be closer to a explaining why ophidiophobia ranks among the top fears of humans, and seems to be shared with other primates.

Researchers inserted probes into the brains of Japanese macacques and found that neurons in a part of their brain that controls visual attention were more strongly and quickly activated in response to images of snakes, versus other objects.

The results, published online Monday in the journal Proceedings of the National Academy of Sciences, appear to support a theory that early primates developed advanced perception as an evolutionary response to being prey, not as an adaptation that may have made foraging or hunting easier.

Though fear of snakes may not be innate, noticing them more than other phenomena may be hard-wired by evolution, said Lynne Isbell, an evolutionary biologist from UC Davis and one of the authors of the paper. That heightened attention, research has shown, can lead to early and resilient learned behavior, such as fear-mediated avoidance. In other words, getting out of the way of snakes.

“The characteristics we have help us to see them better than other mammals can see them,” Isbell said. “Mammals in general are really good at picking up movement. But snakes lie in wait. They don’t move very much, so it’s crucial to see them before they see us and to avoid them.”

Developing new additions to the brain would have given ancestor primates an advantage. Many scientists assumed the advantage had to do with catching insects for food. But Isbell shook that view of primate evolution in 2006, eventually elaborating on it in a book, “The Fruit, the Tree and the Serpent: Why We see So Well.” An arms race between predator and prey is what selected for bigger-brained primates, Isbell argued.

“They were actually prey,” Isbell said “And the first of the modern predators of primates, and the most persistent, that continued to this day -- and that look the same as they did 100 million years ago -- are snakes.”

The brain addition that made all the difference for Old World monkeys was the pulvinar nuclei, according to Isbell. Those areas of the thalamus have been found to control such things as eye and head motions toward stimuli -- responses known as selective spatial attention.

Researchers were probing deep into the limbic system, a region of emotional processing and memory that sometimes is called the old mammalian brain. They inserted probes into the pulvinar nuclei. These nuclei receive inputs directly from the retina of the eye and also connect with nearby brain regions associated with threat-relevant behavior and emotional processing.

Electrical pulses from the pulvinar neurons occurred about 60 microseconds after the snake was presented to the monkeys -- suggesting that the signal might be processed unconsciously. Another pulse came at about 250 microseconds, and that could be associated with feedback from the cortex, where higher cognitive functions are controlled.
The researchers used two monkeys raised in captivity that had no opportunity to encounter a snake. Probes measured responses to snakes, faces and hands of monkeys, and geometric shapes. More neurons responded to the snakes, and did so with greater strength and speed, the data showed.

In addition to those at UC Davis, the research team included scientists from the University of Toyama in Japan and the Primate Center of the University of Brasilia in Brazil. It was supported by the Asian CORE program, which promotes research cooperation.

I don't know where to start, so let's try, this is really weak "science".

Researchers inserted probes into the brains of Japanese macacques and found that neurons in a part of their brain that controls visual attention were more strongly and quickly activated in response to images of snakes, versus other objects.

I stopped reading right here and jumped ahead to discover that this was accomplished with two monkeys (they like to call them subjects in the literature).

I love snakes. I don't like to almost step on them in the woods, but there's something intrinsically beautiful about a creature without feet that can navigate the world the way snakes do.

Timber rattlesnake sleeping in the sun.

This is a timber rattler I came upon while hiking on Bear Mountain in New York (rattlers in NY--who knew?). She didn't budge when I walked within 2 feet of her.

A month later on the same trail, she slithered next to the trail I was walking (about 6 feet away from me) for 100 yards or so...like she was following me. Seemed to be extremely curious and not threatened in the slightest by human presence.

I love you, too, Reilly, LOL! but I was not anthropomorphisizing here. Just a statement of facts. She never once lifted her rattle, or curled in the slightest (signs of agitation). Stayed straight as an arrow and just kept following me, occasionally lifting her head to sample the air with her tongue.

When I veered off the trail, she followed. Only lost her because I was walking faster than she was crawling.

Well, just like my Black Rat, you guys were just having some quality time.
And while few would ascribe a high level of consciousness to snakes I would
be the first to debate that. It is pretty unusual for a rattler to be out
and about so blazenly in the daytime. But then a lot of easterners exhibit
odd behavior regularly. There actually are herpes who believe that rattlers
are being selectively bred out of rattling prophylactively because if you
rattle you are more likely to come to grief from a humanoid.

Here'a a friend I made on Mt Baldy this summer. He was little inclined to
rattle also but then you and I know that is because he knew he was with a
friend. ;-)

Yes, I totally believe that many animals can sense when they're with friend or foe. Some just acclimatized like the JTree rattlesnakes (one lived at the base of Rubicon forever...you just had to step around him to start the climb). Others, like this little frog I found in our jacuzzi, just decide they like you and that's that.

Hope you don't mind, but I'm just gonna hang out on this nice shoulder here until the water temp gets down below 100. Capiche?

Evolution?
BAH!
I'm not afraid of snakes (much) ergo I'm not descended from apes. Proof that Darwin was wrong.

Prettiest snake I've ever seen, a ring necked snake. About the diameter of a pencil about 8" long. All black on top, bright orange beneath with dark orange collar. Found him trying to crawl under my garage door. Took him gently out into the woods where hopefully he couldn't get in quite so much trouble.

Snakes are good neighbors. This King Snake hangs in the yard and comes out for a visit every now and again.

We had a painter over who was totally wigged out by snakes. This guy was hanging out in front of his truck and the painter was apoplectic. Snake was totally calm and I just picked him up and took to a another part of yard. Sure enough it came back and hung out in front of the truck and waited for him again. It was fascinated by the truck for some reason.